Add default namespace check.
Add default namespace check.

sferik/libxml-ruby,xml4r/libxml-ruby,sferik/libxml-ruby,increments/libxml-ruby,sferik/libxml-ruby,xml4r/libxml-ruby,sferik/libxml-ruby,increments/libxml-ruby,sferik/libxml-ruby,increments/libxml-ruby,xml4r/libxml-ruby,sferik/libxml-ruby